Process for preparing 2-(alkylbenzoyl)benzoic acid

Abstract

An environmentally acceptable process is provided to synthesize a 2-(alkylbenzoyl)benzoic acid suitable for synthesizing a 2-alkylanthraquinone without further purification. Usually the crude product is isolated from the reaction mixture by a succession of steps which generate a large volume of aqueous waste. The present process eliminates or decreases these wastes and produces a product of sufficient purity for synthesizing as 2-alkylanthraquinone.

We claim: 
     
       1. A process for synthesizing a 2-(alkylbenzoyl)benzoic acid without generating a large quantity of aqueous waste comprising incorporating phthalic anhydride, an alkylbenzene and aluminum chloride into an inert solvent thereby forming a reaction mixture, maintaining the temperature of the reaction mixture between 0° C. and 90° C. for a sufficient time to react at least part of the phthalic anhydride and alkylbenzene to form a 2-(alkylbenzoyl)benzoic acid in the reaction mixture, combining the reaction mixture and an aqueous, dilute acid thereby forming an aqueous phase and an organic phase, separating the organic phase and the aqueous phase, combining the organic phase with a solvent quantity of a low boiling aliphatic hydrocarbon solvent to precipitate the (alkylbenzoyl)benzoic acid as a solid phase in the combined solvent-organic phase, and separating the solid phase from the solvent-organic phase. 
     
     
       2. The process of claim 1 wherein the low boiling aliphatic hydrocarbon solvent is petroleum ether. 
     
     
       3. The process of claim 1 wherein the alkyl group of the alkylbenzene contains from 1 to 5 carbon atoms. 
     
     
       4. The process of claim 2 wherein the alkyl group of the alkylbenzene contains from 1 to 5 carbon atoms. 
     
     
       5. A process for decreasing the aqueous wastes generated by recovering an 2-(alkylbenzoyl)benzoic acid from a reaction mixture prepared by incorporating phthalic anhydride, an alkylbenzene and aluminum chloride into an inert solvent thereby forming a reaction mixture, maintaining the temperature of the reaction mixture between 0° C. and 90° C. for a sufficient time to react at least part of the phthalic anhydride and alkylbenzene comprising combining the reaction mixture and an aqueous, dilute acid thereby forming an aqueous phase and an organic phase, separating the organic phase and the aqueous phase, combining the organic phase with a solvent quantity of a low boiling aliphatic hydrocarbon solvent to precipitate the (alkylbenzoyl)benzoic acid as a solid phase in the combined solvent-organic phase, and separating the solid phase from the solvent-organic phase. 
     
     
       6. The process of claim 5 wherein the low boiling aliphatic hydrocarbon solvent is petroleum ether. 
     
     
       7. The process of claim 5 wherein the alkyl group of the alkylbenzene contains from 1 to 5 carbon atoms. 
     
     
       8. The process of claim 6 wherein the alkyl group of the alkylbenzene contains from 1 to 5 carbon atoms.